[clang] [CIR] Intitial upstreaming of LibOpt pass (PR #172487)

[Andy Kaylor via cfe-commits]

================
@@ -114,10 +114,14 @@ class CIRGenConsumer : public clang::ASTConsumer {
     mlir::MLIRContext &MlirCtx = Gen->getMLIRContext();
 
     if (!FEOptions.ClangIRDisablePasses) {
+      std::string libOptOptions = FEOptions.clangIRLibOptOptions;
----------------
andykaylor wrote:

```suggestion
      std::string LibOptOptions = FEOptions.clangIRLibOptOptions;
```
Because this file is outside of the CIR directory structure, we follow Clang rules for variable naming.

https://github.com/llvm/llvm-project/pull/172487